1. Field of the Invention
The present invention relates to a scroll thrust bearing, and more particularly to a structure of a scroll thrust bearing having a plurality of both-end conical rollers as rolling elements, and preferably used for thrust force support structure in, for example, a scroll type compressor.
2. Description of the Related Art
The scroll type compressor is a kind of rotary compressors, and it is small in size and free of valve mechanism, and fluid compression is continuous, and as compared with the conventional reciprocating compressors, torque fluctuations and vibrations are small and high speed operation is possible, and hence it is recently applied widely.
This type of compressor has a thrust force support structure for enabling scroll driving. The support structure composes a kind of thrust bearing, and steel balls or other spheres are used as rolling elements. However, such spheres are supported in point contact, and are inferior in durability, not withstanding for long in the conditions of high speed and heavy load, and there were problems in life and others.
To solve these problems, a scroll type compressor having a thrust force support structure as shown in FIG. 28(a) has been proposed (for example, Japanese Laid-open Utility Model No. 61-82086 and Japanese Laid-open Patent No. 62-107284).
The scroll of this compressor is composed as shown in the drawing, that is, a fixed scroll member (c) having a volute (b) is fixed in a housing (a), and a swirl scroll member (e) having a volute (d) engaged with the volute (b) is supported by a thrust force support structure (f) so as to be free to swirl or revolve, and this swirl scroll member (e) is driven and coupled to a drive source not shown through a crankpin (g).
The support structure (f) is formed as a kind of thrust bearing, and a plurality of pockets (h), (i) are disposed oppositely, at the inner side of the housing (a) and the confronting side of the swirl scroll member (e), and both-end conical rolling elements, that is, so-called both-end conical rollers K are freely disposed between the both pockets (h) and (i).
By the rotary drive of the crankpin (g), the swirl scroll member (e) swirls or revolves without rotating about the fixed scroll member (c), and therefore the fluid gas sucked in through a suction port (j) is compressed in a compression chamber formed between the volutes (b) and (d), and is discharged through a discharge port K.
In this case, each both-end conical roller K captured between the pockets (h), (i) makes a rolling motion in linear contact state with flat bottoms (m), (n) of the pockets (h), (i) at its conical surfaces (Ka), (Kb) as schematically shown in FIG. 28(b). These both-end conical rollers K, (R), . . . arrest relative rotation of the both scroll members (c), (e) when the swirl scroll member (e) swirls on the fixed scroll member (c) (the swirl route coincides with the route indicated by arrow (o) in FIG. 28(b)).
According to the thrust force support structure (f) having such both-end conical rollers K, K, . . . , as compared with the conventional structure using spherical rolling elements, the durability is enhanced by far, and it withstands operation at high speed and heavy load for a long period.
In spite of such excellent durability, however, the scroll type compressor having such thrust force support structure (f) is not realized yet mainly because the assembling and manufacturing technology of the thrust force support structure (f) is not established yet.
Specifically, since the scroll swirl radius in the scroll structure of the compressor, that is, the radius of the swirl route (o) in the thrust force support structure (f) is equal to the generator length of conical surfaces (Ka), (Kb) of the both-end conical roller K, the size of the both-end conical roller K itself is very small owing to its structural reason. Besides, in the thrust force support structure (f) of the scroll swirl unit shown in FIG. 28(a), a relative dimensional precision of high level and a high assembling precision are required between constituent elements. On the other hand, as a machine element, mass productivity is also demanded in this kind of thrust force support structure (f).
In such structure, however, in the assembling process of the scroll structure and assembling process into the scroll structure, only a slight vibration may disturb the configuration of the both-end conical rollers K, K, . . . . It is hence difficult to array all both-end conical rollers K, K, . . . in a specific direction and assemble into the track, and mass production by automatic assembling is not yet perfect structurally.
Further, as mentioned above, the both-end conical roller K itself is advantageous in that the load capacity is larger than in the conventional spherical rolling element, but in the both-end conical rollers K actually assembled in the scroll type compressor, since there is a relation with other bearing constituent members, there has been a room for further improvement in the load capacity and durability.